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What do kidney stones and the search for life on Mars have in common? According to Professor Hojatollah Vali, the answer is biomineralization — the formation of minerals by living organisms. "The key to understanding biomineralization is to apply techniques from physical and biological sciences," explains Vali, whose research includes investigating minerals from sources as diverse as Martian meteorites, bacteria and the human body.
In 1996, Vali jointly appointed to the Department of Earth and Planetary Sciences and the Department of Anatomy and Cell Biology, studied a 4.5 billion-year-old Martian meteorite for signs of ancient life as a member of a NASA team. This potato-sized chunk of Mars hurtled across the solar system and eventually smashed into Antarctica. At the newly established Facility for Electron Microscopy Research lab at McGill, of which Vali is director, he examined grains of magnetite in the meteorite and hypothesized these grains could be evidence of Martian bacteria. Vali explains, "Some bacteria produce magnetite grains by biomineralization and leave behind a chain of magnetite materials when they die.
"These bacteria are called magnetotactic bacteria, and one theory is that they use these magnetic minerals as a kind of internal compass to find favourable habitats. The presence of magnetite grains in the meteorite suggests that life may have existed on Mars more than half a billion years before the oldest evidence of life on Earth."
Vali is interested in how these primitive bacteria can form the magnetite grains, and thinks that this type of biomineralization also has implications for the evolution of life. The magnetotactic bacteria, like all bacteria, belong to a primitive group called prokaryotes. Vali's recent collaboration with researchers from the California Institute of Technology reveals that these bacteria grow the magnetite biominerals inside membrane-bound compartments within the cell. These functional compartments are normally associated with eukaryotes, a higher evolutionary group, and are rarely found in prokaryotes. The presence of these compartments in prokaryotic magnetotactic bacteria suggests that they may be the "missing link" between primitive prokaryotes and more evolved eukaryotes, and represent a critical stage in the evolution of life.
Vali and his colleagues at McGill also study biomineralization inside and outside human cells. Humans need biomineralization for bone formation, but unfortunately, the body also produces harmful biominerals, such as kidney stones. Vali explains, "In the traditional view of mammalian biomineralization, minerals precipitate outside of cells." However, from his investigation of tissue from a dysfunctional human liver, he showed that a biomineral similar to bone precipitated inside the liver cells. "The liver had almost become a rock," he explains. Vali and his colleagues are amongst the first researchers to show biomineralization inside human cells. In the future, Vali hopes to identify the proteins or agents responsible for this type of potentially fatal, intracellular human biomineralization. If successful, this would be a large step in the development of drugs that could prevent this type of harmful biomineralization.
The success of Vali's multidisciplinary approach to biomineralization is because of his ability to bridge gaps between geology, biology and medicine. Consequently, his research appeals to a range of scientists — and of course, to anyone who dreams of Martians, or has ever passed a kidney stone.
Sponsored by the Faculty of Science, the Offices of the Vice-Principal (Research) and University Relations, NSERC, the Faculty of Engineering and the Faculty of Agriculture and Environmental Sciences. See www.spark.mcgill.ca for more information and articles.